https://www.youtube.com/watch?
I didn't have the money to get the aluminium sheet at $105.00AUD each (at Masters) and I needed two so I came up with the next best thing, a roll of Hardaz Vermin Wire Mesh 6.5X6.5mm, 15cmx10M roll for about $20.00AUD. It wasn't wide enough so I modified it by soldering two lengths together and it almost came out at the correct size, so close it didn't matter to me anyway. Now to make a CONE is a bit tricky and it took me a few goes with big sheets of paper first but it worked okay in the end, mind you it isn't pretty but it tests perfectly electrically and works very well.
The top and bottom formers are 10mm MDF and the three supports are good quality dowel, I also cut out some curved MDF to hold the wire in the centre and as circular as possible, you can just see one of them to the right of the centre dowel on the bottom former. All the dimensions are in the video for the wire and you will need to design your own support frame. As I said it isn't perfect, even a bit wonky but it works very well. The RTL.SDR comes with a Small antenna and simply didn't work at all in my location so I made up a 2M coaxial co liner dipole with three elements and it works fantastically on the amateur band but not much good above and below that. The bi-conical was picking up hundreds of automotive RF remote door lock transmitters on my first try, amazing to listen to, yes I'm nuts I know, also I was listening to aircraft coming and going from Sydney airport and I live in Bathurst, on a big hill and I look towards Sydney from my yard and I couldn't do that on the original antenna or the coaxial antenna so if you want to build a cheap antenna that works amazingly this is the one for you. By the way get it up as high as possible and it will blow you away I'm sure, it did me.
PS. I forgot to mention that I got the RTL.SDR so I could receive and play with the Cubesat, Amsat and othersat's out there so I will be building a yargi or two to get good signals for them and most of the sensors have arrived for the Arduino home based sat so more on that later as well.
